1. Field of the Invention
The present invention relates to a space photovoltaic power generation system for receiving sunlight in space so as to generate electric power, for transmitting the electric power to an electric power base via space by converting the electric power to a microwave, and for storing the electric power in the electric power base so as to allow the use of the electric power, and a power satellite and a control satellite for use with the system.
2. Description of the Prior Art
A solar cell is known as a small-size power generation system which utilizes sunlight. Furthermore, a photovoltaic power generation panel or the like, which can be set up on a building, is known as a power generation system intended for the home which utilizes sunlight. Such a photovoltaic power generation system built on the earth""s ground is not necessarily efficient fundamentally because of the attenuation of sunlight in the earth""s atmosphere and the alternation between shade and light caused by the alternation between day and night. A solar panel, which can be installed in a satellite, is known as a photovoltaic power generation device intended for space. Satellites can thus achieve missions by privately generating necessary electric power for observation and communications, etc. by using a solar panel. In either of the prior art power generation systems, specific equipment connected to the solar cell by cable is adapted to use the energy generated by the solar cell.
On the other hand, as the communication technology progresses according to results of recent space development works and the construction technology to construct a large-scale space structure progresses, research and development of a system that receives sunlight in space, generates electric power, and transmits the generated energy to a specific place such as a specific location on the earth or in space has been actively conducted. An example of such a space photovoltaic power generation system can focus sunlight, thereby increasing the energy density of the sunlight, to a number of solar panels each having a specific size and connected mechanically and electrically to each other, for photoelectric-converting the incident sunlight so as to generate electric power, by using a combination of reflectors, lenses, etc., and then generates a microwave based on the generated energy and transmits the microwave to an electric power base built on the earth""s ground. The microwave transmitted to the ground is spread over a range wide so that its energy density becomes small in consideration of safety. The electric power base built on the earth""s ground includes a number of receiving antennas arranged in an area of several tens of square kilometers, receives incident microwaves by means of these receiving antennas, and integrates the received microwaves into high electric power.
In the prior art space photovoltaic power generation system as mentioned above, a large-scale electric power generation and transmission structure can be constructed in space by adding a number of solar cells to a transmission antenna and microwave generation equipment arranged in space as the core of the system. However, a problem with the prior art space photovoltaic power generation system constructed as above is that since the electric power from the plurality of solar cells fundamentally concentrates on the microwave generation equipment and the transmission antenna, both a limit on the electric power transmission due to a discharge breakdown that occurs in a power supply line and a limit on the amplification capability of the microwave generation equipment impose a limit on the power generation capacity of the space photovoltaic power generation system.
The present invention is proposed to solve the above-mentioned problem. It is therefore an object of the present invention to provide a space photovoltaic power generation system capable of transmitting electric power generated in space from sunlight to an electric power base so that the electric power is dispersed without concentrating the electric power generated to a point on the electric power base, and a power satellite and a control satellite for use with the system.
In accordance with an aspect of the present invention, there is provided a space photovoltaic power generation system comprising: a plurality of power satellites each for generating electrical energy from sunlight in space, for generating a microwave from the generated electrical energy, and for transmitting the microwave; an electric power base located at a remote site for receiving a plurality of microwaves transmitted from the plurality of power satellites, and for generating electric power from the plurality of microwaves received; and a control unit for controlling the plurality of power satellites so that the plurality of microwaves transmitted from the plurality of power satellites to the electric power base are in phase with one another.
In accordance with a preferred embodiment of the present invention, the control unit includes a location measurement unit for measuring a location of each of the plurality of power satellites, a phase adjustment amount calculation unit for calculating an amount of phase adjustment to be made to the microwave which each of the plurality of power satellites will transmit from the measured location, and a phase control unit for adjusting a phase of the microwave which each of the plurality of power satellites will transmit according to the amount of phase adjustment calculated by the phase adjustment amount calculation unit so that the plurality of microwaves transmitted from the plurality of power satellites to the electric power base are in phase with one another.
Preferably, the space photovoltaic power generation system further comprises a control satellite including the location measurement unit, the phase adjustment amount calculation unit, and a transmission unit for informing each of the plurality of power satellites of the amount of phase adjustment calculated for each of the plurality of power satellites. Each of the plurality of power satellites can include a receiving unit for receiving the amount of phase adjustment from the control satellite, a target for enabling the control unit to measure the location of each of the plurality of power satellites, a condensing unit for focusing sunlight in space, a photoelectric conversion unit for receiving and converting the sunlight focused by the condensing unit into electrical energy, and a transmission unit that also serves as the phase control unit, for generating a microwave based on the electrical energy from the photoelectric conversion unit, for adjusting the phase of the microwave according to the amount of phase adjustment received by the receiving unit, and for transmitting the microwave to the electric power base. The location measurement unit of the control satellite can be a unit for measuring the location of each of the plurality of power satellites using the target disposed in each of the plurality of power satellites, and the transmission unit of the control satellite can be a unit for transmitting a control signal including the amount of phase adjustment calculated by the phase adjustment amount calculation unit to each of the plurality of power satellites.
As an alternative, the space photovoltaic power generation system can further comprise a control satellite including the location measurement unit, and a transmission unit for informing each of the plurality of power satellites of data on the location of each of the plurality of power satellites measured by the location measurement unit. In addition, each of the plurality of power satellites can include the phase adjustment amount calculation unit and the phase control unit, and adjusts the phase of the microwave which each of the plurality of power satellites will transmit so that the microwave is in phase with any other microwave transmitted from any other one of the plurality of power satellites according to the calculated amount of phase adjustment. Each of the plurality of power satellites can include a target for enabling the location measurement unit of the control unit to measure the location of each of the plurality of power satellites, a condensing unit for focusing sunlight in space, a photoelectric conversion unit for receiving and converting the sunlight focused by the condensing unit into electrical energy, and a transmission unit that also serves the phase control unit, for generating a microwave based on the electrical energy from the photoelectric conversion unit, for adjusting the phase of the microwave according to the amount of phase adjustment calculated by the phase adjustment amount calculation unit, and for transmitting the microwave to the electric power base. The location measurement unit of the control satellite can be a unit for measuring the location of each of the plurality of power satellites using the target disposed in each of the plurality of power satellites, and the transmission unit of the control satellite can be a unit for transmitting a control signal including data on the location of each of the plurality of power satellites measured by the location measurement unit to each of the plurality of power satellites.
In accordance with another preferred embodiment of the present invention, the control unit transmits an identical reference signal to each of the plurality of power satellites, and each of the plurality of power satellites generates a microwave based on the reference signal received and transmits the microwave to the electric power base.
In accordance with a further preferred embodiment of the present invention, the electric power base includes a transmission unit for transmitting a beacon signal to the control satellite, a receiving unit for receiving the plurality of microwaves transmitted from the plurality of power satellites, a microwave-to-DC conversion unit for converting the plurality of microwaves received by the receiving unit into DC electric power, and a DC electric power transmission unit for transmitting the DC electric power obtained by the microwave-to-DC conversion unit.
In accordance with another aspect of the present invention, there is provided a power satellite comprising: a condensing unit for focusing sunlight in space; a photoelectric conversion unit for receiving and converting the sunlight focused by the condensing unit into electrical energy; and a transmission unit for generating a microwave based on the electrical energy from the photoelectric conversion unit, for adjusting a phase of the microwave so that the microwave is in phase with any other microwave transmitted by any other power satellite, and for transmitting the microwave to space.
In accordance with a further aspect of the present invention, there is provided a control satellite comprising: a location measurement unit for measuring a location of each of a plurality of power satellites, each of which generates a microwave from sunlight in space and transmits the microwave, by using a target disposed in each of the plurality of power satellites; a phase adjustment amount calculation unit for calculating an amount of phase adjustment to be made to the microwave which each of the plurality of power satellites will transmit from the location of each of the plurality of power satellites measured by the location measurement unit; and a transmission unit for transmitting a control signal including the amount of phase adjustment calculated by the phase adjustment amount calculation unit to each of the plurality of power satellites.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.